An essential component for adequate immune regulation is lymphocyte recirculation which ensures the exposure of effector cells to antigen. The distribution of lymphocytes in lymphoid tissues is regulated by selective binding of lymphocytes to high endothelial venule (HEV) cells. HEV cells may also play a role in trapping of lymphomas and metastatic cancer cells in lymph nodes, or dissemination of tumors through the lymphatic system. Information about the mechanisms whereby HEV cells control lymphocyte recirculation will provide a basis towards proposing interventions in diseases with abnormal lymphocyte recirculation. Although a few cell surface receptors for lymphocyte-HEV cell binding have been identified, the mechanisms for the regulation of lymphocyte recirculation are not understood. Our HEV cell lines, from mouse brachial (HEVb) and cervical (HEVc) lymph nodes, offer a unique opportunity to perform, for the first time, a systematic analysis of the role of surface molecules, cytokines, and biochemical events necessary for lymphocyte binding to and migration across HEV cell layers. The HEVb and HEVc cell lines have been subcloned by limiting dilution since they consist of at least two morphologically different cell populations. The clones which exhibit common characteristics of HEV cells (non-specific esterase activity, MECA-325 expression, binding of mature lymphocytes, and incorporation of 33S into sulfated glycoproteins) will be selected for the remainder of the studies. The HEV cell clones shall be phenotypically characterized using antibodies against HEV surface adhesion molecules. The HEV and lymphocyte cell surface molecules involved in the binding of distinct lymphocyte subsets to the HEVb and HEVc cell clones will be determined by pretreating HEV cells and lymphocytes with appropriate monoclonal antibodies, or a combination thereof. The cell surface molecules involved in lymphocyte migration through HEV cell monolayers on transwell membranes will be determined by antibody- inhibition studies. The role of the cell filaments actin and tubulin as well as the role of cytokines and antigens in lymphocyte binding to and migration across monolayers of the HEV cell clones will be evaluated. Future goals are to determine whether a) comitogenic signals are delivered to lymphocytes by lymphocyte-HEV cell binding, b) whether HEV cells present antigen to lymphocytes since HEV cells endocytose antigen and express class II MHC molecules, and c) whether binding activates intracellular second messengers in HEV cells or lymphocytes.